The prior art has included a number of rotating and reciprocating air motors useable to drive hydraulic pumps and the like. One such air motor is described in U.S. Pat. No. 3,272,081(Vedder, et al.) entitled Air Motor, the entirety of which is expressly incorporated herein by reference.
One drawback associated with at least some of the reciprocating air motors of the prior art, including that described in U.S. Pat. No. 3,272,081, is that slide valve(s) within the air motor ride in metal to metal contact with valve sleeve(s) or other parts of the apparatus and continual lubrication must be dispensed into, such metal to metal interface to avoid excessive wear of the piston(s) and to maintain a reasonable service life for the air motor. Additionally, the slide valve(s) and sleeve(s) or other parts between which the metal to metal fit is required must be precisely machined for a high tolerance fit and are typically required to be made of hard. machinable metal such as stainless steel. The application of lubricant upon the engaged metal surfaces was typically accomplished by atomizing oil in the air that is used within the air motor such that the atomized oil will deposit on the piston(s) and other parts of the air motor apparatus that frictionally interface with the piston(s). However, when the air exhausts from the air motor, some amount of atomized oil typically remains in the exhausted air and presents a health risk to workers who incur long term respiratory exposure to the said atomized oil that is exhausted by the air motor. Additionally, the use of atomized oil in the air can be laborious, cumbersome and adds expense to the operation in which it is used.
In view of the foregoing, there exists a need in the art for the development of an oilless reciprocating air motor of the type described in U.S. Pat. No. 3,272,081 wherein self lubricating or lubricious materials are positioned between the slide valve(s) and valve sleeve(s) or other portions of the air motor that frictionally interface with the slide valve(s), thereby eliminating the need for precisely machined, high tolerance fits between such parts and also eliminating the need for the use of atomized oil, other added oil or grease or added lubricant during routine operation of the air motor.